Thermal battery with encapsulated phase-change material

ABSTRACT

The present invention relates to a thermal battery having an enclosure (2) containing a bundle (3) comprising tubes (3′) of encapsulated phase change material, the bundle (3) being formed by a stack of banks of tubes (3′), said banks comprising tubes (3′) placed parallel to one another and being connected by bracing and supporting bars (5), said bars (5) comprising, on at least one of their faces, individual housings separated from one another by a lateral wall, each housing being capable of receiving one tube (3′).

The present invention relates to the field of thermal batteries, and more precisely that of thermal batteries comprising a phase change material.

Thermal batteries are generally used for heating passenger compartments, notably in electric and hybrid vehicles, or for preheating a heat transfer fluid in a thermal management circuit. Thermal batteries may also be used for preheating the engine oil or automatic gearbox oil in vehicles with internal combustion engines.

A thermal battery with a phase change material usually comprises an enclosure forming a reservoir, in which the phase change material, usually in encapsulated form, notably in the form of tubes forming a bundle, is placed. The performance of the thermal battery depends on the amount of phase change material that it can contain, that is to say the number of tubes present in the bundle, but also on the contact surface area between the fluid passing through the thermal battery and said tubes. The tubes must therefore be kept at a certain distance from one another, so that the fluid passing through the thermal battery can circulate. However, the tubes must also be fairly close together in order to incorporate the largest possible amount of phase change material into the thermal battery, to make the battery efficient.

For example, there is a known way of keeping the phase change material tubes at a certain distance from one another by means of braces or by means of a porous, foam-like material through which a fluid can pass. However, these solutions are usually expensive and difficult to include in an industrial process, or generate large pressure drops in the fluid, leading to reduced efficiency of the thermal battery.

One of the objects of the present invention is therefore to overcome at least some of the drawbacks of the prior art, and to propose an improved thermal battery.

Accordingly, the present invention relates to a thermal battery having an enclosure comprising a fluid inlet and outlet, and containing a bundle comprising tubes of encapsulated phase change material, the bundle being formed by a stack of banks of tubes, said banks comprising tubes placed parallel to one another and being connected by bracing and supporting bars, said bars comprising, on at least one of their faces, individual housings separated from one another by a lateral wall, each housing being capable of receiving one tube.

The bars allow a high degree of modularity in the design of thermal batteries, while also enabling the production costs to be reduced. Furthermore, the use of such bars enables the tubes to be correctly supported and arranged with respect to one another, so as to form a bundle, while limiting the pressure drops of the fluid passing through the bundle.

According to one aspect of the invention, the spacing between the tubes within one bank is defined by the width of the lateral wall between two housings.

According to another aspect of the invention, the housings have a shape complementary to that of the tubes, and an insertion opening smaller than the tube diameter, so that said tubes can be clipped into the housings.

According to another aspect of the invention, the bars of successive banks are placed in a quincuncial arrangement on planes parallel to one another and perpendicular to the tubes.

Thus the bars between two successive banks do not lie above one another, and allow the fluid to flow between the tubes without an excessive pressure drop.

According to another aspect of the invention, the bars of successive banks are grouped on two parallel planes, separated by a distance at least greater than the width of the bars.

According to another aspect of the invention, the bundle is contained in a frame.

According to another aspect of the invention, the frame comprises flanges surrounding the bundle and external braces connecting said brackets.

According to another aspect of the invention, the flanges comprise grooves into which bars are inserted.

According to another aspect of the invention, the banks comprise internal braces between the bars.

According to another aspect of the invention, the banks are flat.

According to another aspect of the invention, the bundle is cylindrical and the banks are curved and concentric.

According to another aspect of the invention, the bars comprise housings on two of their opposed faces, so as to support two superimposed banks, the spacing between said banks being defined by the thickness of the wall of said bars separating the housings located on either side of the bars.

According to another aspect of the invention, the housings on one face of the bars and the housings on the other face of said bars are placed in a quincuncial arrangement.

According to another aspect of the invention, the bars comprise housings on only one of their faces.

According to another aspect of the invention, the tubes of two successive banks are placed in a quincuncial arrangement, the tubes of the upper bank resting on the lateral wall of the bar of the lower bank, the spacing between the tubes of said banks being defined by the height of said lateral wall.

Other characteristics and advantages of the invention will be more clearly apparent from a reading of the following description, provided as an illustrative and non-limiting example, and from the appended drawings, among which:

FIG. 1 shows a schematic perspective exploded view of a thermal battery,

FIG. 2 shows a schematic view in longitudinal section of the thermal battery of FIG. 1,

FIG. 3 shows a schematic view in cross section of a stack of banks,

FIG. 4 shows a schematic perspective view of a tube bundle,

FIG. 5 shows a schematic exploded perspective view of a tube bundle,

FIG. 6 shows a schematic perspective view of a portion of a bar according to a first embodiment,

FIGS. 7a and 7b show schematic views, transverse and longitudinal respectively, of a superimposition of banks with bars of FIG. 6,

FIG. 8 shows a schematic perspective view of the assembly of the tube bundle with a flange,

FIG. 9 shows a schematic perspective view of a portion of a bar according to a second embodiment,

FIGS. 10a and 10b show schematic views, transverse and longitudinal respectively, of a stack of banks with bars of FIG. 9,

FIG. 11 shows a schematic view in cross section of a stack of banks according to an alternative embodiment.

In the various figures, identical elements bear the same reference numerals.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference concerns the same embodiment, or that the characteristics are applicable to a single embodiment only. Simple characteristics of different embodiments may also be combined to provide other embodiments.

FIGS. 1 and 2 show a schematic view of a thermal battery 1 comprising an enclosure 2 in which a fluid flows between a fluid inlet 2 a and outlet 2 b. The thermal battery 1 comprises, within the enclosure 2, a bundle 3 composed of tubes 3′ of phase change material. The tubes 3′ of the bundle 3 are positioned parallel to one another. The bundle 3 may, for example, be inserted into the enclosure 2 through an opening 2 c. Said opening 2 c is closed after the insertion of the bundle 3 by a cover 2 d.

The bundle 3 is positioned parallel to the circulating flow of the fluid in the enclosure 2. The tubes 3′ of phase change material each comprise a tubular wall, preferably made of plastic material, for example polycarbonate, in which a phase change material is positioned. The tubular wall is closed in a sealed way at the ends of the tubes 3′.

As shown in greater detail in FIGS. 3 and 4, the bundle 3 is formed by a stack of banks 4 of tubes 3′. These banks 4 comprise tubes 3′ placed parallel to one another and connected by bracing and supporting bars 5.

The bars 5 may be straight, as shown in FIG. 3. In this case, the banks 4 are flat and may be stacked on one another. The length L of the bars 5 of a bank 4 determines the width of the latter, and the shape of the bundle 3 may thus be varied by modifying the length L of the bars 5 and consequently the width of the banks 4 from one to another. An example of a bundle 3 of generally cylindrical shape is thus shown in FIGS. 1 to 5. However, other shapes of the bundle 3, parallelepipedal for example, are possible and imaginable.

The bars 5 are shown in greater detail in FIGS. 6 to 7 b. Said bars 5 comprise, on at least one of their faces, individual housings 50 separated from one another by a lateral wall 51. The housings 50 are each intended to receive a tube 3′, so as to form the bank 4. The spacing between the tubes 3′ within a bank 4 is, notably, defined by the width Lp of the lateral wall 51 between two housings 50.

To support the tubes 3′ correctly, the housings 50 may have a shape complementary to that of said tubes 3′, and may have an insertion opening 52 smaller than the diameter of the tubes 3′, so that said tubes 3′ can be clipped into the housings 50. In this case, the lateral walls 51 are resilient and may be deformed and move away from one another to enable a tube 3′ to be inserted into the housing 50. When the tube 3′ has been inserted, the lateral walls 51 return to their initial position and partially grip the tube 3′ in order to lock it.

It would also be feasible for the bars 5 to comprise closed housings 50 into which the tubes 3′ are fitted. The bars 5 may, for example, be overmoulded around the tubes 3′ so as to form the banks 4.

The bars 5 are preferably made of plastic material and may be manufactured in a long strip which is cut to the desired length L according to the shape and size of the thermal battery 1.

Thus the bars 5 allow a high degree of modularity in the design of the thermal batteries, while also enabling the production costs to be reduced. Furthermore, the use of such bars 5 enables the tubes 3′ to be correctly supported and arranged with respect to one another so as to form a bundle 3, while limiting the pressure drops of the fluid passing through the bundle.

According to a first embodiment shown in FIGS. 6 to 7 b, the bars 5 may comprise housings 50 on two of their opposed faces. One bar 5 may thus support the tubes 3′ of two superimposed banks 4, one on each of its faces. The spacing between the banks 4 is then defined by the thickness E of the wall of said bars 5 separating said housings 50 located on either side of the bars 5. Preferably, to facilitate the flow of the fluid, while also optimizing the number of tubes 3′, the housings 50 on one face of the bars 5 and the housings 50 on the other face of said bars 5 are placed in a quincuncial arrangement.

In this case, and in the rest of the patent application, the term “placed in a quincuncial arrangement” is taken to mean a repeated arrangement of elements, row by row, in which one of every two rows is offset by a certain amount, notably by half of an element, relative to the row preceding or following it.

The bars 5 of successive banks 4 are preferably placed in a quincuncial arrangement on planes parallel to one another and perpendicular to the tubes 3′, as shown in FIG. 7b . Thus the bars 5 between two successive banks 4 do not lie above one another, and allow the fluid, the flow of which is indicated by two black arrows, to circulate between the tubes 3′ without an excessive pressure drop.

Since one bar 5 supports two superimposed banks 4, all the banks 4 are supported together, enabling the cohesion and shape of the bundle 3 to be maintained.

Preferably, in a cross section of the bundle 3, the bars 5 of successive banks 4 may be grouped on two parallel planes and separated by a distance D which is at least greater than the width Lb of the bars 5, so that the bars 5 are not adjacent, thus allowing the fluid to flow as shown in FIG. 7b . Said bars 5 then form a supporting assembly 6. Over its length, the bundle 3 may comprise a plurality of supporting assemblies 6. These supporting assemblies 6 are also visible in FIGS. 2 and 5.

According to a second embodiment shown in FIGS. 8 to 10 b, the bars 5 may comprise housings 50 on only one of their faces. By contrast with the first embodiment, a bar 5 can only support the tubes 3′ of a single bank 4. Preferably, in this second embodiment, the tubes 3′ of two successive banks 4 are placed in a quincuncial arrangement as shown in FIG. 10a , in order to facilitate the flow of the fluid while also optimizing the number of tubes 3′. The tubes 3′ of the upper bank 4 can thus rest on the lateral wall 51 of the bar 5 of the lower bank 4. The spacing between the tubes 3′ of said banks 4 is then defined by the height Hp of said lateral wall 51, corresponding to the distance between the base and the end of said lateral wall 51.

As in the first embodiment, the bars 5 of successive banks 4 are preferably placed in a quincuncial arrangement on planes parallel to one another and perpendicular to the tubes 3′, as shown in FIG. 10b . Thus the bars 5 between two successive banks 4 do not lie above one another, and allow the fluid, the flow of which is indicated by two black arrows, to circulate between the tubes 3′ without an excessive pressure drop. Similarly, in a cross section of the bundle 3, the bars 5 may be grouped on two parallel planes separated by a distance D at least greater than the width Lb of the bars 5, so that the bars 5 are not adjacent, thus allowing the flow of the fluid as shown in FIG. 7b . Said bars 5 then form a supporting assembly 6. Over its length, the bundle 3 may comprise a plurality of supporting assemblies 6. These supporting assemblies 6 are also visible in FIGS. 2 and 5.

Preferably, the bundle 3 comprises at least one supporting assembly 6 at each of its ends, and at least one intermediate supporting assembly 6 between said ends. This permits a constant separation of the banks 4 from one another, and therefore a constant spacing of the tubes 3′ over the whole length of the bundle 3. In the example shown in FIGS. 1, 2, 4 and 6, the bundle 3 comprises a total of four supporting assemblies 6.

The bundle 3 may also comprise internal braces 41, visible in FIGS. 4 and 5, within the banks 4. These internal braces 41 may be, more particularly, solid rigid tubes made of plastic or metal and may, notably, each take the place of a tube 3′ in a bank 4, so that they are clipped into the housings 50 of the bars 5. These internal braces 41 make it possible to stiffen the banks 4, while keeping the bars 5 at a certain distance from one another. These internal braces 41 also make it possible to maintain the cohesion of the supporting assemblies 6 and to maintain the spacing between them. At the positions of the bars 5, the internal braces 41 may have grooves 42, corresponding to a reduction in the cross section of the internal brace 41. These grooves 42 are inserted into the housings 50 of the bars 5. Thus any translational movements of said bars 5 along the tubes 3′ and relative to one other are prevented.

The bundle 3 is preferably contained in a frame 7, as shown in FIGS. 1, 2, 4 and 5. This frame 7 makes it possible, notably, to consolidate the shaping of the bundle 3 and reinforce its strength. The frame 7 also makes it possible to provide a degree of rigidity in the bundle 3. The frame 7 may, notably, comprise flanges 70 surrounding the bundle 3 transversely, and external braces 71 connecting said flanges 70. The flanges 70 and the external braces 71 may be made of metal and/or plastic.

As shown in FIG. 8, the flanges 70 may also comprise grooves 701 into which the bars 5 are to be inserted. More particularly, these grooves 701 allow said bars 5 to be connected to the frame 7 so as to keep said bars 5 in place, independently of the fact that they can be clipped on to the tubes 3′ and independently of the possible presence of internal braces 41. If the banks 4 are flat, it is the ends of the different bars 5 that are inserted into the grooves 701. The flanges 70 may then comprise at least two parallel grooves 701, and may be placed at the positions of the supporting assemblies 6.

In order to facilitate the assembly and production of bundles 3, the latter may be assembled into two half-bundles which are placed adjacent to one another. The half-bundles may, for example, be assembled and fastened together, for example by means of male/female fastening devices present at the positions of the flanges 70.

Instead of being flat, the banks 4 may be curved and stacked concentrically, so as to form a cylindrical bundle 3, as shown in FIG. 11. However, in order to limit the stresses on the bars 5, particularly those due to the radius of curvature, it is preferable to form a bundle 3 by stacking flat banks 4.

If the banks 4 are curved and concentric, the use of a frame 7 makes it possible, notably, to maintain the curvature of said banks 4 as well as the cylindrical shape of the bundle 3. In this example, and notably if the bars 5 have housings 50 on only one of their faces, it is the back, that is to say the part not having a housing 50, of the bars 5 of the outer bank 4 that is inserted into the grooves 701 of the flanges 70.

Evidently, therefore, by using bars 5 to form braces between the tubes 3′ and organize them into banks 4, it is easier to assemble the bundles 3 for the purpose of manufacturing thermal batteries 1. 

1. A thermal battery comprising: an enclosure comprising a fluid inlet and outlet, and containing a bundle comprising tubes of encapsulated phase change material, wherein the bundle is formed by a stack of banks of tubes, said banks comprising tubes placed parallel to one another and being connected by bracing and supporting bars, said bars comprising, on at least one of their faces, individual housings separated from one another by a lateral wall, each housing being capable of receiving one tube.
 2. The thermal battery as claimed in claim 1, wherein the separation between the tubes within a bank is defined by the width of the lateral wall between two housings.
 3. The thermal battery as claimed in claim 1, wherein the housings have a shape complementary to that of the tubes, and have an insertion opening smaller than the diameter of the tubes, so that said tubes are clipped into the housings.
 4. The thermal battery as claimed in claim 1, wherein the bars of successive banks are placed in a quincuncial arrangement on planes parallel to one another and perpendicular to the tubes.
 5. The thermal battery as claimed in claim 4, wherein the bars of successive banks are grouped on two parallel planes and separated by a distance which is at least greater than the width of the bars.
 6. The thermal battery as claimed in claim 1, wherein the bundle is contained in a frame.
 7. The thermal battery as claimed in claim 6, wherein the frame comprises flanges surrounding the bundle and external braces connecting said flanges.
 8. The thermal battery as claimed in claim 7, wherein the flanges comprise grooves into which bars are inserted.
 9. The thermal battery as claimed in claim 1, wherein the banks comprise internal braces between the bars.
 10. The thermal battery as claimed in claim 1, wherein the banks are flat.
 11. The thermal battery as claimed in claim 1, wherein the bundle is cylindrical and the banks are curved and concentric.
 12. The thermal battery as claimed in claim 1, wherein the bars comprise housings on two of their opposed faces, so as to support two superimposed banks, the spacing between said banks being defined by a thickness of the wall of said bars separating the housings located on either side of the bars.
 13. The thermal battery as claimed in claim 12, wherein the housings on one face of the bars and the housings on the other face of said bars are placed in a quincuncial arrangement.
 14. The thermal battery as claimed in claim 1, wherein the bars comprise housings on only one of their faces.
 15. The thermal battery as claimed in claim 14, wherein the tubes of two successive banks are placed in a quincuncial arrangement, the tubes of the upper bank resting on the lateral wall of the bar of the lower bank, the spacing between the tubes of said banks being defined by the height of said lateral wall. 